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From "Robert Engels" <>
Subject RE: NioFile cache performance
Date Fri, 09 Dec 2005 16:58:23 GMT
That is why "guarantee" is in quotes. Any OS worth its salt should end up
caching a "massively read" 4mb file (unless you are running on an OS with
1mb or memory). If the file was 400mb, you probably have a different story.

I welcome (and would hope) others to run the tests on various OSs and
various hardware configs.

I would expect similar results on other platforms, as most of the
improvement is due to keeping the machine in user context and avoiding
context switches to OS level code.

-----Original Message-----
From: John Haxby []
Sent: Friday, December 09, 2005 4:24 AM
Subject: Re: NioFile cache performance

Robert Engels wrote:

> Using a 4mb file (so I could be "guarantee" the disk data would be in
> the OS cache as well), the test shows the following results.

Which OS?   If it's Linux, what kernel version and distro?   What
hardware (disk type, controller etc).

It's important to know: I/O (and caching) is very different between
Linux 2.4 and 2.6.   The choice of I/O scheduler can also make a
significant difference on 2.6, depending on the workload.   The type of
disk and its controller is also important -- and when you get really
picky, the mobo model number.

I don't dispute your finding for a second, but it would be good to run
the same test on other platforms to get comparative data: not least
because you can get the kind of I/O time improvement you're seeing on
some workloads on different versions of the Linux kernel.


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